I had the same problem until I removed the second and third row of rubber bumpers from the bottom of the seat pan. The 2nd row are about 1/4" thick, but the third row are big rubber blocks. Now I don't have the sliding forward sensation any longer, and the seat is a bit more comfortable too.
This sounds like an easy fix but with the bumpers off will the seat pan not make contact with the wiring, fuses or other components under there, if not I would be willing to give it a try. Just seems to me that the rubber bumpers would be there to keep the seat up and off those important parts.